Effects of peach orchard soil on plant growth and photosynthetic fluorescence characteristics of Fuji apple

Abstract:【Objective】The phenomenon of transforming peach orchard into apple orchard is common in production. However, the components in the previous soil are complex, and their impact on the subsequent plants cannot be predicted. There have been few reports on the impact of the peach orchard soil on the growth and fruiting of the later crop of apple trees. The Fuji / Malus robusta plants were selected as the test materials. The effects of peach orchard soil on the plant growth characteristics, leaf protective enzymes, leaf photosynthetic fluorescence parameters of apple trees, the yield and quality of Fuji apples were studied.【Methods】The effects of peach orchard soil on the growth, photosynthesis, yield and quality of Fuji apples were studied under field conditions. The treatment was apple trees planted in the peach orchard soil. The control was apple trees planted in the farmland soil nearby. The indexes of apple plant growth characteristics included plant height, trunk girth, crown width, new shoot length, germination rate, branching rate, short branch rate, flower branch rate and internode length, etc. The related indexes of apple leaves included leaf area, leaf fresh mass, chlorophyll (a+b) content, net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), intercellular carbon dioxide concentra-tion (Ci), actual PSⅡ efficiency (ΦPSⅡ), efficiency of light energy capture by open PSⅡ reaction centers (Fv’/Fm’), non- photochemical quenching of PSⅡ (NPQ), quantum yield of PSⅡ electron transport (ETR), photochemical quenching of PSⅡ (qP), superoxide dismutase, peroxidase, catalase and ascorbic acid peroxidase, membrane permeability, hydrogen peroxide, superoxide ion, soluble sugar and proline. The related indexes of apple quality included fruit hardness, fruit shape index, smoothness, coloring index and sugar acid. The active potassium content, active phosphorus content, total N content, organic matter content and pH value of soil were also tested.【Results】Compared with the control, the crown width, new shoot length, branching rate and internode length of apple trees planted in the peach orchard soil decreased significantly by 13.1%, 19.8%, 8.8% and 11.1% respectively. There was no significant difference in plant height, trunk girth, germination rate, short branch rate and flowering branch rate between the treatment and control. The peach orchard soil inhibited the growth of apple trees and shortened the internode length of new shoots. Compared with the control, the leaf area and leaf fresh of apple trees planted in the peach orchard soil decreased significantly by 17.6% and 7.2% respectively, the content of protective enzymes in the leaves decreased in various degrees, the activities of superoxide dismutase, peroxidase, catalase and ascorbic acid peroxidase decreased significantly by 8.8%, 21.5%, 18.3% and 22.8%, the contents of MDA, H2O2, O2 ¯ , soluble sugar and proline increased significantly by 17.0%, 19.4%, 45.5%, 19.4% and 25.9%, the activity of antioxidant enzymes in the apple leaves decreased, the content of reactive oxygen species increased, the degree of lipid membrane peroxidation increased, and the contents of soluble sugar and free proline increased, the net photosynthetic rate, Fv’/Fm’, ΦPSⅡ and ETR decreased significantly by 12.1%, 20.3%, 30.0% and 35.5%, respectively, the 1-qP and NPQ were significantly increased by 60% and 41.3%, respectively. There was no significant difference in chlorophyll content, transpiration rate, stomatal conductance and intercellular CO2 concen tration. Under the condition of peach orchard soil, the photochemical activity of PSⅡ reaction center in the apple leaves decreased, the electron transport chain was damaged, the actual photochemical efficiency decreased, and the closing degree of PSⅡ reaction center in the leaves increased, resulting in the weakening of electron receiving ability on the receptor side, increasing the excitation pressure on PSⅡ, and changing the distribution mode of PSⅡ excitation energy in the apple leaves. Under the conditions of peach orchard soil, the yields per 666.7 m2 of the apple trees in 2017—2021 were significantly lower than those of the control, the ratio of decrese were 15.7%-32.3%. The degree of skin finish and sugaracid ratio of the apple fruits were significantly lower than those of the control, the ratio of decrease were 7.9% and 23.8% respectively. There was no significant difference in fruit firmness, fruit shape index, color index, soluble solid content, soluble sugar content, and titratable acid content. There were no significant difference in active potassium content, active phosphorus content, total N content, organic matter content and pH value of soil between the treatment and CK.【Conclusion】Peach orchard soil inhibited the growth of apple trees, reduced branching rate, shortened the internode length of the new shoots, reduced the activity and photochemical activity of the PSⅡ reaction center, destroyed the electron transport chain, reduced the excitation energy capture efficiency, the actual photochemical efficiency, the net photosynthetic rate, and the antioxidant enzyme activity of the leaves to various degrees. The dynamic balance between the antioxidant enzyme system and reactive oxygen species of the apple trees planted in the peach orchard soil was broken, the contents of soluble sugars and proline in the leaves in creased, fruit yield, sugar-acid ratio and degree of skin finish decreased.